This application corresponds to Korean patent application No. 97-28144 filed Jun. 27, 1997, in the name of Samsung Electronics Co., Ltd., which is herein incorporated by reference for all purposes.
1. Field of the Invention
This invention relates generally to semiconductor devices, and more particularly, to a method for forming a silicon-oxynitride layer suitable for use as a gate insulating layer on a semiconductor device.
2. Description of the Related Art
A layer of silicon oxide is generally used as gate insulation for semiconductor memory devices. However, as semiconductor devices become more highly integrated, the silicon oxide layer must be made thinner, and thus, the electric field strength in the gate insulation increases. Accordingly, the leakage current, breakdown voltage, and other characteristics of the silicon oxide layer must be improved to maintain adequate performance at a given operation voltage.
However, the characteristics of silicon oxide layers can not be improved sufficiently, and thus, silicon oxide is inappropriate for use as gate insulation in highly integrated semiconductor devices.
Accordingly, a need remains for an improved gate insulation layer for semiconductor devices.
Therefore, it is an object of the present invention to provide a gate insulation layer having improved characteristics.
Another object of the present invention is to provide a gate insulation layer for semiconductor device that can replace silicon oxide.
A further object of the present invention is to provide a method for forming an improved gate insulation layer on a semiconductor device.
To accomplish these and other objects, a semiconductor device constructed in accordance with the present invention provides improved performance at high integration levels by utilizing a gate insulation layer formed from silicon-oxynitride which prevents impurities in the doped gate electrode from diffusing into the semiconductor substrate during the fabrication processes.
A method for forming the silicon-oxynitride layer in accordance with the present invention utilizes a vertical diffusion furnace to increase productivity and achieve a uniform nitrogen density in the silicon-oxynitride layer. The method includes forming an initial oxide layer on a semiconductor substrate, changing the initial oxide layer into a pure oxide layer, and then changing the pure oxide layer into a silicon-oxynitride layer. The initial oxide layer is formed by loading a semiconductor substrate into a diffusion furnace at a temperature between 550xcx9c750xc2x0 C., raising the temperature of the substrate to between 700xcx9c950xc2x0 C., and injecting a mixture of oxygen and nitrogen has into the diffusion furnace. The initial oxide layer is then changed into a pure oxide layer by utilizing either a wet or dry oxidation method. The pure oxide layer is then changed into a silicon-oxynitride layer by injecting N2O into the diffusion furnace. Finally, nitrogen gas is injected into the furnace to cool the substrate down slowly, thereby reduce stress in the substrate
One aspect of the present invention is a method for forming a silicon-oxynitride layer on a semiconductor device, the method comprising: (a) forming an initial oxide layer on a semiconductor substrate; (b) changing the initial oxide layer into a pure oxide layer; and (c) changing the pure oxide layer into a silicon-oxynitride layer. Steps (a) through (c) are preferably performed in a vertical diffusion furnace.
Changing the pure oxide layer into a silicon-oxynitride layer can be done by injecting N2O into the diffusion furnace. And the pure oxide layer can be formed by utilizing either a wet or dry oxidation method. The pure oxide layer grows when the initial oxide layer is changed into a pure oxide layer, and the silicon-oxynitride layer grows when the pure oxide layer is changed into the silicon-oxynitride layer.
Another aspect of the present invention is a method for forming a silicon-oxynitride layer on a semiconductor device, the method comprising: loading a semiconductor substrate into a diffusion furnace at a first temperature; injecting nitrogen into the diffusion furnace; raising the temperature of the diffusion furnace including the semiconductor substrate to a second temperature; injecting a mixture of oxygen and nitrogen gas into the diffusion furnace, thereby forming an initial oxide layer on the semiconductor substrate; oxidizing the semiconductor substrate at the second temperature, thereby changing the initial oxide layer into a pure oxide layer; injecting N2O gas into the diffusion furnace, thereby changing the pure oxide layer into a silicon-oxynitride layer; and injecting nitrogen gas into the diffusion furnace, thereby reducing the temperature of the diffusion furnace.
A further aspect of the present invention is a semiconductor device comprising a gate insulation layer formed from silicon-oxynitride.